Many seamless capsules used for medicine or the like have been manufactured by a production method called a dripping method. According to the dripping method, a multiple nozzle is typically used. For a two-layer capsule, what is used is a double nozzle; a discharge opening for a capsule filling substance is placed inside the double nozzle, while a discharge opening for a coating substance is placed outside the double nozzle. The filling substance and the coating substance are released from the tip of each nozzle into a hardening liquid. The released droplet takes a spherical shape because of the surface tension thereof. The droplet is cooled down and solidified in the hardening liquid that circulates at a constant speed. As a result, a spherical seamless capsule is formed.
As for such a seamless capsule manufacturing apparatus, those disclosed in Patent Documents 1 to 3 have been known, for example. For example, what is disclosed in Patent Document 1 is a seamless capsule manufacturing apparatus that uses a multiple nozzle equipped with a vibration exciter. According to the device disclosed in Patent Document 1, the multiple nozzle releases a liquid current for forming a capsule into a hardening liquid. In the hardening liquid, the liquid current is vibrated and divided. Therefore, a multilayer seamless capsule is formed. FIG. 3 is an explanatory diagram showing the configuration of such a conventional seamless capsule manufacturing apparatus.
In the device shown in FIG. 3, a vibration exciter 52 is placed on an upper portion of a multiple nozzle 51. The vibration exciter 52 adds vibrations to the nozzle 51. A core liquid 53 and an outer coating liquid 54 are supplied into the nozzle 51. The core liquid 53 and the outer coating liquid 54 make up a multilayer liquid current 55, which is released into a hardening liquid coolant 56 from a tip portion of the nozzle 51. The liquid coolant 56 is supplied to a liquid coolant inflow section 59 having a double-pipe structure; a capsule forming pipe 57 is placed inside the liquid coolant inflow section 59, and a solution supply pipe 58 outside the liquid coolant inflow section 59. The liquid current 55 released from the nozzle 51 drops into the capsule forming pipe 57. In the capsule forming pipe 57, the liquid current 55 is divided into small multilayer droplets 61 as vibrations are added by the vibration exciter 52. The multilayer droplets 61 move on in the liquid coolant 56 as the liquid coolant 56 flows. At this time, the outer layers of the multilayer droplets 61 become solid in the liquid coolant 56. As a result, multilayer seamless capsules are formed.    Patent Document 1: Jpn. Pat. Appln. Laid-Open Publication No. 9-155183    Patent Document 2: Jpn. Pat. Appln. Laid-Open Publication No. 2000-189495    Patent Document 3: Jpn. Pat. Appln. Laid-Open Publication No. 6-124293
However, according to such a conventional seamless capsule manufacturing apparatus, if the flow volume of the liquid coolant 56 becomes unstable or if the flow of the liquid coolant 56 flowing into the capsule forming pipe 57 becomes unbalanced, there is a fear that the shape of the multilayer droplets 61 might be changed in the capsule forming pipe 57. If the multilayer droplets 61 has deformed, a neatly-formed spherical seamless capsule is not formed. Therefore, the problem is that it is not possible to manufacture spherical capsules in a stable manner.
The object of the present invention is to have the stable flow of the liquid coolant in the capsule forming pipe and manufacture spherical seamless capsules in a stable manner.